Creation of "Time Series - Multiple Line" chart broken

[villebro]

Make sure these boxes are checked before submitting your issue - thank you!

• I have checked the superset logs for python stacktraces and included it here as text if any
• I have reproduced the issue with at least the latest released version of superset
• I have checked the issue tracker for the same issue and I haven't found one similar

Superset version

master

Expected results

Creation of "Time Series - Multiple Line" should work.

Actual results

Nothing happens when clicking on chart type. JS debugger shows the following:

Steps to reproduce

1. Create any chart type
2. Change chart type to "Time Series - Multiple Line"